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My Ktm Sx250f Keeps Getting Hot!

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I don't know why, but my ktm 250f keeps getting hot and shooting the coolant out of the overflow thing and sometime boiling over! And its not like I ride hard for a long time and just let it sit there and idle, it does it while I'm riding hard like after 20 min. of riding hard non-stop! Ive tryed bleeding my anitfreeze and refilling it with ENGINE ICE...its helping a little but its still not normal, ANY SUGGESTIONS? 🙂

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try the two2cool oil additive. but somthing isnt right with the bike b/c mine never runs hot and I ride it 30 mins plus 2 laps on a deeps sand track and its 90+ outside, so idk what ur deal is, but if it keeps doin that ur motor isnt gonna last.

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Mine does not get hot at all. I do know if you slip the clutch much, ti gets hot fast, or if you go slow with no air flow through the radiator it will get hot. Dragging the brakes doesn't help either. If none of the previous mentioned things are happening, then check your cap you should check your cap to see if it is working properly. If that doesn't turn up the problem, then do a pressure test to see if you have any leaks. Good luck

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I don't know why, but my ktm 250f keeps getting hot and shooting the coolant out of the overflow thing and sometime boiling over! And its not like I ride hard for a long time and just let it sit there and idle, it does it while I'm riding hard like after 20 min. of riding hard non-stop! Ive tryed bleeding my anitfreeze and refilling it with ENGINE ICE...its helping a little but its still not normal, ANY SUGGESTIONS? 🙂

I rode in Tight woods today and never had an issue, but I was jetted on the fat side.. I would suggest riching it up a bit and that will most likely go away... just to put twocool2 in at this point would be a band aid- fix the issue first- lean condition...

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Ok thanks alot everyone, I'll have to see if any of that helps, I hope so!

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First thing I would look at is coolant level. You may be over filling the rads and its normal expansion. You should fill it about 1/2" over the tubes.

Next I would check the cap and the filler neck. A small nick in the neck can cause fluid leakage. Once the fluid starts leaking at the small nick it can just grow.

One easy way to help figure boilover out is to stop and squeeze a radiator hose with your fingers. If its crazy tight then it kind of tells you that the excessive pressure is causing the boilover and not a defective cap.

The next thing I would do is look at the plug. I am not a big fan of "jetting for life". In other words if you are jetted correctly and having boilover I wouldnt make the jetting fatter just to help cool the bike.

As far as using two2cool. I have allways stated that two2cool could be used to mask (bandaid) a mechanical issue. But we do not reccomend it.

On the other hand you may be riding at the level that you are a canadate for using two2cool. These bikes can have oil temps well above 300f. I havent tested a 250sx yet but every other 4 stroke motocross bike on the planet can make oil temps in excess of 300f.

If this is the case then you are our target consumer. If you have no way to check your temps next time your bike is loosing coolant then stop and lean it against a tree. Pour a small amount of water, spit, or take a piss on the clutch cover. If it sizzles like crazy then you have excessive oil temperature.

I know I am a target for even mentioning such a scientific test.

This may be due to riding level, riding style or terrain. No cooling system commonly used on offroad bikes helps with this problem at all

If you are making oil temps in excess of 300f adding two2cool will keep this much heat from being generated thus lowering your oil temps. In 4 strokes its common to see a coolant temp drop approx. 1/3 of the oil temp drop.

Thanks Norman

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My 250 SXF will "spit" if I let it idle too long but... In the past I have had a problem with my 520SX if I didn't bleed the air out of the system. It had an area in the head that simply would not clear the air without using the bleeder. It actually says in your manual to check this if overheating is an issue (page 52). The bleeder is on the top of the left radiator which you would think would clear itself of air but this bike does not use a transfer tube between the radiators (my 520SX does) so it could be the problem.

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> RC876 wrote: If you are making oil temps in excess of

> 300f adding two2cool will keep this much heat from being

> generated thus lowering your oil temps. In 4 strokes its

> common to see a coolant temp drop approx. 1/3 of the oil

> temp drop.

>

Two2Cool works... in the short run only.

The boiling point of Two2Cool according to the MSDS (Material

Safety Data Sheet) published (required by U.S. law) by the makers

of Two2Cool , is 375 degrees F. Regular motor oil boils around

550 degrees F.

Two2Cool works by boiling off. When anything boils (goes from a

liquid state to a gas state) it take a tremendous amount of

energy out of the system. This is called the phase-change effect.

The phase-change effect also happens when a substance goes from a

solid to a liquid.

Once any part of your bike's oiled surfaces (think the hot engine

head) reach 375 degrees F. Two2Cool boils taking heat (energy)

out of the engine. The vapors leave via the crankcase vent.

This cooling will happen until the Two2Cool is completely

evaporated.

What damage can this cause? Think of the bubbles generated in a

pot of boiling water. Would you want a bubble (void) of no

lubrication to appear between your engine's cam lobe and rocker

arm?

Besides being extremely cost prohibitive, I doubt you'll find any

professional engine builder out there that recommends putting

*any* substance in your engine's crankcase that boils at 375

degrees F.

Here's a warning I've already sent out to other motorsports

forums:

==========

Date: Wed, 13 Jul 2005 15:47:22 -0400

To: moto.org

From: Russell Stephan

Subject: Two2Cool oil additive.

Maybe you guys have heard about this stuff. The web page is

completely devoid of any "hard" facts about how it works to cool

an engine drastically (like 30 degrees F drastic).

Although the company's owner, one Russell Clay, claims some new

chemical with special heat seeking properties is responsible, a

review of the MSDS (Material Safety Data Sheet) reveals the

additive's boiling point to be 375 degrees F. That's pretty low

to be in with the oil. Oil usually boils around 550 degrees F.

So how does Two2Cool actually work? The low boiling point allows

drastic engine cooling through the well-known process of liquid

to gas phase-change when oil temperatures start nearing the

additive's boiling point. Lots of energy is removed from any

system when a substance goes from solid to liquid or liquid to

gas. The venting of the gas to atmosphere happens through the

crankcase breather.

The cooling effect is drastic but only temporary until the

Two2Cool is completely boiled off from the engine.

Here's the sad part... The owner of the company actually believes

he has discovered some substance that by-passes the traditional

laws of thermodynamics.

Give him about a week to talk with his various experts and

realize the error of his theories. If he hasn't changed his tune

by then, he's snake oiling for dollars on purpose.

The science is well-known to those that paid attention in high

school physics and chemistry. Don't let Mr. Clay's chemical

yammer babble deflect from the very basic idea of the

conservation of energy. The energy in must equal the energy out.

There is no such thing as disappearing heat. Energy can neither

be created nor destroyed. It can only change form.

If you'd like to follow this complete thread check out

www.thumpertalk.com. Go to forums, XR250/400, and look over the

topic "two2cool oil additive". It's extremely long, I know. I'm

going to try and cull my main points out for further

dissemination on the web.

This guy charges an arm and a leg for this stuff. It's pure

bogus.

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its the jetting, richen it up a little and your problem will be solved. I had the exact same problem and richened it up a little and have had no problems since.

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Mr urbandirt has no first hand knowledge of how two2cool works. I have time and time again offered to explain it to him personally on the phone. He has time and time again refused to take me up on the offer.

This only shows he has an agenda. Now he has resorted in finding other threads about two2cool and bashing the product.

I also have a guarantee that no one including Urbandirt has taken us up on. It has been posted here on thumpertalk more than once.

The guarantee is for anyone who wants to take us up on the offer to come whitness a test with two brand new RMZ250's. if the test doesnt go as we say it will we will give bother bikes to you. We do more into detail and offer to let you conduct the test.

Again Urbandirts decision not to come collect the free bikes only goes to show he has an agenda.

Now from a personal standpoint I think his actions are nothing more than a coward and think he is a chickenshit.

Anyone else having questions or concers please feel free to contact us, 863 357 3400 Norman

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I just purchased a 525EXC and experienced overheating the first two times out. Dropped it by the dealer last week and they told me it was due to the stock KTM jetting. That KTM uses very lean jetting to get by US EPA standards, which have a reputation of running very lean on fuel causing them to backfire (pop), and run really hot. My overheating happen just the same way...spewing out of the puke hose from the neck of the radiator. Just got the bike back from the shop, so I haven't ridden yet on the new jetting. Stay tuned...Good Luck!

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Bleed it outa the head not the radiator. Common problem. It should not overheat. Sounds like bleeding to me for it to spit out that much coolant

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First you must blead the air out of the head, second you must blead the right radiator, third you must not fill the left one more than 10mm in the top tank, bike level. Failure to do so and it will burp coolant probubly long before opporating temp.

The carb is jetted too lean and jets will not fix it, the needle has too little taper, JD's kit is hte best answer but they can run OK with an OCEMN needle, its kinda frustrating conversion as the OCEMN has so much taper that it effect the main jet (need about 158) so the JD is my choice.

I have heard enough about the too cool to suspect it does as claimed, I would not be a good test as i have had no overheat problems.

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